问题
How would I go about rotating a Bitmap in Windows GDI,C++?
回答1:
You can do it with GDI+ (#include <gdiplus.h>). The Graphics class has the RotateTransform method. That allows arbitrary rotations. Use Image::RotateFlip() if you only need to rotate by 90 degree increments, that's a lot more efficient.
回答2:
Sounds like you have to use PlgBlt. Take your rectangle's 4 corners as 2D Points, rotate them, then call PlgBlt.
From MSDN Bitmap Rotation:
To copy a bitmap into a parallelogram; use the PlgBlt function, which performs a bit-block transfer from a rectangle in a source device context into a parallelogram in a destination device context. To rotate the bitmap, an application must provide the coordinates, in world units, to be used for the corners of the parallelogram.
回答3:
Another possibility (beyond those already suggested) is to use SetWorldTransform(). This is different in that it is modal and applies to the DC as a whole, not just a single operation. If you want to rotate one bitmap rotated, but other things without rotation, it's probably not your best choice. If you want to draw a number of things rotated, or (especially) if you want to rotate everything you draw (at least into one DC) it can work quite nicely though.
来源：https://stackoverflow.com/questions/2270110/how-to-rotate-bitmap-in-windows-gdi